From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6A46C31E51 for ; Tue, 18 Jun 2019 06:52:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BBBEB20673 for ; Tue, 18 Jun 2019 06:52:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=neuling.org header.i=@neuling.org header.b="Tz1x9QBm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728942AbfFRGwY (ORCPT ); Tue, 18 Jun 2019 02:52:24 -0400 Received: from ozlabs.org ([203.11.71.1]:36515 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726676AbfFRGwX (ORCPT ); Tue, 18 Jun 2019 02:52:23 -0400 Received: from neuling.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 45Sd9C3hMDz9sNk; Tue, 18 Jun 2019 16:15:11 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=neuling.org; s=201811; t=1560838511; bh=SXPCd1WoGf+poGC7TcVU//uBUHMfckPpSH22kDTOs88=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Tz1x9QBmql6pHgCR0xXLI6o8RUYhTE/51mro8K5ulnDbbGXV/dwg3nEZGalqQG0gF rQef7ubbJY4GQr0l6ogbgm11VQaqyf7cOWLIZPfKQhlLMIU/nY+PKnZIicZ3QHj7J7 /BfI0ZRHL+XTZbZFav5+pwlmhXmptQxTG2ZiRlxgdeem+Tq9lEvM+w7UHmVlb84skh tyUnGDg1b4PRh95dqUcD3ImI9fyyNiMxNNUxC/Pbuia/5Mp90lsGJ6AcUlSrMC2ZgV RYFGV3chAW3D7XNH/QPzwAiH9esFG8m5kcekq6Vnf/nfc5HPjUpKV5WGKbnSNaWmqw 2Q1DskdwiWk3A== Received: by neuling.org (Postfix, from userid 1000) id 664B12A2538; Tue, 18 Jun 2019 16:15:11 +1000 (AEST) Message-ID: Subject: Re: [PATCH 4/5] Powerpc/hw-breakpoint: Optimize disable path From: Michael Neuling To: Ravi Bangoria , mpe@ellerman.id.au Cc: benh@kernel.crashing.org, paulus@samba.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, christophe.leroy@c-s.fr, naveen.n.rao@linux.vnet.ibm.com Date: Tue, 18 Jun 2019 16:15:11 +1000 In-Reply-To: <20190618042732.5582-5-ravi.bangoria@linux.ibm.com> References: <20190618042732.5582-1-ravi.bangoria@linux.ibm.com> <20190618042732.5582-5-ravi.bangoria@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.32.2 (3.32.2-1.fc30) MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2019-06-18 at 09:57 +0530, Ravi Bangoria wrote: > Directly setting dawr and dawrx with 0 should be enough to > disable watchpoint. No need to reset individual bits in > variable and then set in hw. This seems like a pointless optimisation to me.=20 I'm all for adding more code/complexity if it buys us some performance, but= I can't imagine this is a fast path (nor have you stated any performance benefits).=20 Mikey >=20 > Signed-off-by: Ravi Bangoria > --- > arch/powerpc/include/asm/hw_breakpoint.h | 3 ++- > arch/powerpc/kernel/process.c | 12 ++++++++++++ > 2 files changed, 14 insertions(+), 1 deletion(-) >=20 > diff --git a/arch/powerpc/include/asm/hw_breakpoint.h > b/arch/powerpc/include/asm/hw_breakpoint.h > index 78202d5fb13a..8acbbdd4a2d5 100644 > --- a/arch/powerpc/include/asm/hw_breakpoint.h > +++ b/arch/powerpc/include/asm/hw_breakpoint.h > @@ -19,6 +19,7 @@ struct arch_hw_breakpoint { > /* Note: Don't change the the first 6 bits below as they are in the same > order > * as the dabr and dabrx. > */ > +#define HW_BRK_TYPE_DISABLE 0x00 > #define HW_BRK_TYPE_READ 0x01 > #define HW_BRK_TYPE_WRITE 0x02 > #define HW_BRK_TYPE_TRANSLATE 0x04 > @@ -68,7 +69,7 @@ static inline void hw_breakpoint_disable(void) > struct arch_hw_breakpoint brk; > =20 > brk.address =3D 0; > - brk.type =3D 0; > + brk.type =3D HW_BRK_TYPE_DISABLE; > brk.len =3D 0; > if (ppc_breakpoint_available()) > __set_breakpoint(&brk); > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.= c > index f002d2ffff86..265fac9fb3a4 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -793,10 +793,22 @@ static inline int set_dabr(struct arch_hw_breakpoin= t > *brk) > return __set_dabr(dabr, dabrx); > } > =20 > +static int disable_dawr(void) > +{ > + if (ppc_md.set_dawr) > + return ppc_md.set_dawr(0, 0); > + > + mtspr(SPRN_DAWRX, 0); > + return 0; > +} > + > int set_dawr(struct arch_hw_breakpoint *brk) > { > unsigned long dawr, dawrx, mrd; > =20 > + if (brk->type =3D=3D HW_BRK_TYPE_DISABLE) > + return disable_dawr(); > + > dawr =3D brk->address; > =20 > dawrx =3D (brk->type & HW_BRK_TYPE_RDWR) << (63 - 58);